Gasification monitor, method for detecting mist, film forming method and film forming apparatus

ABSTRACT

A deposition apparatus supplies a reactive gas obtained by vaporizing a liquid material at a vaporizer  30  into a chamber  10  via a processing-gas pipe  40  and forms a thin film on a semiconductor wafer W due to a thermal decomposition of the reactive gas. The deposition apparatus is provided, in the processing-gas pipe  40 , with a crystal gauge  51  detecting a pressure Pq under the influence of mist in the reactive gas and a capacitance manometer  52  detecting a pressure Pg under no influence of the mist. The apparatus further includes a gasification monitor  50  detecting a quantity of mist in the reactive gas on the basis of a difference ΔP between the pressure Pq and the pressure Pg measured by the crystal gauge  51  and the capacitance manometer  52  in order to prevent deposition defects due to the mist in the reactive gas.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a gasification monitor, a method for detectingmist, a film forming method and a film forming apparatus, which areapplicable to a technique where, for example, a liquid material or asolid material is vaporized and supplied into a chamber to perform adesignated processing, such as chemical vapor deposition (CVD).

2. Background Art

In order to manufacture a desired semiconductor device, generally, thereare repeatedly carried out a film deposition process and a patternetching process against a semiconductor wafer. With high integration andhigh-density of semiconductor devices, the specifications of depositiontechnique are becoming increasingly severe every year. For instance,even for an oxidation film of great thinness (e.g. insulation film, gateinsulation film, etc. of a capacitor in a device), an electrode film anda wiring film, it is required to reduce the film-thickness of thesefilms furthermore. Giving an example of a gate insulation film, a methodfor forming HfO₂-film, ZrO₂-film, SiO₂-film by MOCVD (Metal OrganicChemical Vapor Deposition) method is proposed. In the above method,organic metallic compounds, such as Hf(OtBu)₄, Zr(OtBu)₄ and SiH(NMe₂)₃,are used as deposition materials. However, it should be noted that allof these materials are liquids at ambient temperatures and haverespective vapor pressures of relative lowness at temperatures less thantheir resolving temperatures. Therefore, Japanese Unexamined PatentPublication (kokai) No. 2001-148347 discloses a method where thesematerials are vaporized in a vaporizer and continuously, the resultantvapor is introduced, as a processing gas, into a deposition chamber forfilm deposition due to the thermal decomposition of the vapor.

In the MOCVD method mentioned above, there is a worry that if theevaporation of liquid material is incomplete in the vaporizer, theliquid material in the form of mist in a processing gas is transportedthe chamber, so that the liquid materials may adhere to a thin film on asubstrate.

Meanwhile, the vaporizer disclosed in the above publication (kokai) No.2001-148347 is provided with a variety of ingenious plans in order toperform its vaporization effectively. Nevertheless, the same publication(kokai) No. 2001-148347 does not make arrangements to detect the mistincluded in the processing gas to be supplied into the chamber. Thus, itis impossible to detect deposition defects due to the mist unless a thinfilm has been deposited on a substrate practically.

Additionally, since it takes a long time to inspect defects after thedeposition, it is difficult to take prompt measures to meet thesituation, causing the productivity of a deposition process to belowered.

SUMMARY OF THE INVENTION

In the above-mentioned situation, it is an object of the presentinvention to provide a technique enabling a prevention of film formingdefects due to mist contained in the processing gas etc.

Further, it is another object of the present invention to provide atechnique enabling an improvement of the productivity of a film formingprocess where a film forming is carried out by a processing gas producedin a vaporizer.

In order to solve the above-mentioned objects, the first feature of thepresent invention resides in the provision of a gasification monitorarranged in a gas feeding path between a vaporizer for vaporizing aliquid material or a solid material to producing a processing and aprocessing part where the processing gas is used, the gasificationmonitor detecting a quantity of mist contained in the processing gas.

The second feature of the invention resides in the provision of a mistdetecting method for detecting mist contained in a gas, comprising thesteps of: detecting a first pressure Pq of the gas, which is changeableby a quantity of mist contained in the gas, by a first method; detectinga second pressure Pg of the gas, which is unchangeable by the quantityof mist contained in the gas, by a second method; and detecting thequantity of mist contained in the gas on a basis of a difference ΔPbetween the first pressure Pq detected by the first method and thesecond pressure Pg detected by the second method.

The third feature of the invention resides in the provision of a filmforming method for forming a thin film on an object to be processed bythermally decomposing a processing gas obtained by vaporizing a liquidmaterial or a solid material, the film forming method comprising thesteps of: monitoring a quantity of mist contained in the processing gas;and controlling vaporizing conditions of the liquid material or thesolid material in a manner that the quantity of mist decreases.

The fourth feature of the invention resides in the provision of a filmforming method for forming a thin film on an object to be processed bythermally decomposing a processing gas obtained by vaporizing a liquidmaterial or a solid material, the film forming method comprising thesteps of: monitoring a quantity of mist contained in the processing gas;and either outputting a warning or stopping a deposition process whenthe quantity of mist exceeds a predetermined threshold value.

The fifth feature of the invention resides in the provision of a filmforming apparatus comprising: a processing part for forming a thin filmon an object to be processed by use of a processing gas; a vaporizer forvaporizing a liquid material or a solid material to supply theprocessing part with the processing gas; and a gasification monitorarranged in a gas feeding path for the processing gas between thevaporizer and the processing part, for detecting a quantity of mistcontained in the processing gas.

In the first to fifth aspects of the present invention, as the detectingmeans for detecting the quantity of mist contained in the processinggas, it is possible to adopt a gasification monitor including: a firstpressure gauge for detecting the pressure Pq of the processing gas byuse of a fact that a impedance of the oscillator arranged in theprocessing gas changes dependently of the pressure of the processinggas, a second pressure gauge for detecting the pressure Pg of theprocessing gas on a basis of a deformation of the pressoreceptive partsubjected to the pressure of the processing gas, and a control part fordetecting the quantity of mist contained in the processing gas on abasis of a difference ΔP between the first pressure Pq detected by thefirst pressure gauge and the second pressure Pg detected by the secondpressure gauge.

Further, as the first pressure gauge, it is possible to adopt a crystalgauge that detects the first pressure Pq of the processing gas by usinga quartz oscillator as the oscillator. As the second pressure gauge, itis possible to adopt a capacitance manometer that includes a diaphragmas the pressoreceptive part and electrodes opposing the diaphragm andthat detects the second pressure Pg of the processing gas by detecting adeformation of the diaphragm in the form of a change in electrostaticcapacity between the diaphragm and the electrodes.

Thus, utilizing a fact that a change in pressure of the environmentabout the first pressure gauge allows a friction between the quartzoscillator and a gaseous molecule to be changed so that an impedance ofoscillation of the quartz oscillator varies, the crystal gauge (as thefirst pressure gauge) measures the change in impedance of oscillationand further converts it to a pressure. Therefore, if a mist larger thanthe gaseous molecule is present, then the friction between the quartsoscillator and the gaseous molecule with the mist causes the crystalgauge to detect a value larger than an actual pressure in proportion toa quantity of the mist.

On the other hand, in the capacitance manometer (as the second pressuregauge), even if a mist is contained in a gas to be measured, there is nochange in measured values of pressure since the capacitance manometer isconstructed so as to detect a pressure due to a deformation of thediaphragm.

Accordingly, if only calibrating the operations of both of the crystalgauge and the capacitance manometer so that, in the absence of mist,their measured values are identical to each other within a desiredmeasurement range, then it becomes possible to measure the quantity ofmist by calculating a difference between their measured values.

In the first and fifth aspects of the present invention, the processingpart is adapted so as to form a thin film on an object to be processedby use of a thermal decomposition of the processing gas.

In the fifth aspect of the present invention, the film forming apparatusfurther comprises a process controller that controls at least either oneof the operation of the vaporizer and the operation of the processingpart, on a basis of the quantity of mist obtained by the gasificationmonitor.

In the first to fifth aspects of the present invention, the processinggas is an organic metallic compound.

In this way, according to the present invention, it is possible tomeasure a quantity of mist contained in the processing gas in situ.Therefore, if performing various controls, for example, a control wherethe measured result of the quantity of mist is fed back to the controlsof various vaporizing conditions in the vaporizer, thereby suppressingthe quantity of mist to a low value causing no film forming defect, acontrol where an outside operator is informed of the occurrence of mist,a control where the film forming process is automatically stopped whenthe quantity of mist is more than a predetermined threshold value, etc.,then it becomes possible to prevent an occurrence of film formingdefects due to the mist contained in the processing gas, certainly.

Consequently, it becomes possible to measure the film forming defectsquickly in comparison with a countermeasure where an object to beprocessed is inspected after the film forming process in order to detectfilm forming defects due to mist, whereby the productivity at the filmforming process can be improved.

According to the present invention, it is possible to prevent anoccurrence of film forming defects due to mist contained in theprocessing gas or the like. Additionally, it is possible to improve theproductivity of a film forming process using a processing gas producedin a vaporizer.

These and other objects and features of the present invention willbecome more fully apparent from the following description and appendedclaims taken in conjunction with the accompany drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing a deposition apparatus to carry out adeposition method in accordance with an embodiment of the presentinvention;

FIG. 2 is a sectional view showing one example of a vaporizer of thedeposition apparatus of the embodiment of the present invention;

FIG. 3 is a flow chart showing one example of the operation of agasification monitor in the deposition apparatus of the embodiment ofthe present invention;

FIG. 4 is a flow chart showing one example of the operation of a processcontroller in the deposition apparatus of the embodiment of the presentinvention;

FIG. 5 is a perspective view showing one example of a crystal gaugeforming the gasification monitor of the deposition apparatus of theembodiment of the present invention; and

FIG. 6 is a sectional view showing one example of a capacitancemanometer forming the gasification monitor of the deposition apparatusof the embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

An embodiment of the present invention will be described with referenceto accompanying drawings.

FIG. 1 illustrates a deposition apparatus for carrying out a depositionmethod in accordance with one embodiment of the present invention. Byway of example, the deposition apparatus is provided to form a HF(hafnium) oxidation film by means of CVD (chemical vapor deposition).The deposition apparatus includes a chamber 10 forming a processing partof the apparatus, a liquid-material source 20 for supplying a liquidmaterial containing HF, a vaporizer 30 for vaporizing the liquidmaterial from liquid-material source 20 to produce a processing gas anda processing-gas pipe (gas feeding path) 40 for introducing theso-produced processing gas into the chamber 10.

The chamber 10 is cylindrical-shaped and constructed so as to allow itspumping to a vacuum. Disposed in the chamber 10 is a susceptor 11 thatsupports a semiconductor wafer W as an object to be processed,horizontally. In the chamber 10, the susceptor 11 is supported by aplurality of cylindrical support members 12 (only one shown in thefigure). A heater 14 is embedded in the susceptor 11. By electricitysupplied from a power source 15, the heater 14 is capable of heating thesemiconductor wafer W as the object to be processed, to a predeterminedtemperature. A process controller 16 is connected to the power source15. Consequently, corresponding to signals from a temperature sensor(not shown), the output to the heater 14 is controlled by the processcontroller 16.

An exhaust port 17 is formed in a bottom wall 10 b of the chamber 10.The exhaust port 17 is connected to an exhaust system 18. By the exhaustsystem 18, the chamber 10 can be depressurized to a designated vacuum.

A shower head 19 is attached to a top wall 10 a of the chamber 10. Theprocessing-gas pipe 40 is connected to the shower head 19 through a feedcontrol valve 19 a. With such an arrangement, the processing gasvaporized in the vaporizer 30 is introduced into the shower head 19. Theshower head 19 is provided with an inner space 19 b. Additionally, theshower head 19 is provided, on its surface opposing the susceptor 11,with a number of gas discharging holes 19 c. Thus, reactive gasintroduced into the inner space 19 b of the shower head 19 through theprocessing-gas pipe 40 is discharged from the gas discharging holes 19 cto the semiconductor wafer W on the susceptor 11.

As illustrated in FIG. 2, the vaporizer 30 of this embodiment includes amain body 31 defining a vaporizing space 32 therein, a vaporizing heater33 and a vaporizing heater 34 both arranged so as to surround thevaporizing space 32. A vaporizing nozzle 35 is arranged at one end ofthe vaporizing space 32 coaxially. The vaporizing nozzle 35 is connectedto the liquid-material source 20 through a material flow-control valve35 a and a material pipe 20 a.

A nozzle space 32 a is formed in the circumference of the tip of thevaporizing nozzle 35. Communicated with the nozzle space 32 a is acarrier-gas passage 38 that is connected to an exterior carrier-gassource through a carrier-gas pipe 36 and a carrier-gas control valve 37.

In the lateral part of the main body 31, a gas passage 39 is formed tocommunicate the vaporizing space 32 with the processing-gas pipe 40.

In operation, the introduction of carrier gas, such as nitrogen gas,into the nozzle space 32 a while spraying the liquid material into thevaporizing space 32 via the vaporizing nozzle 35 allows the liquidmaterial to be dispersed in the vaporizing space 32 and vaporized intoreactive gas. Then, the reactive gas is mixed with the carrier gas andthe resultant processing gas is transferred from the gas passage 39 tothe processing-gas pipe 40.

In the vaporizer 30, according to the situations, there is a possibilitythat the liquid material vaporizes incompletely. Consequently, part ofthe liquid material is changed to fine mist and transferred to theprocessing-gas pipe 40 and the chamber 10, together with the materialgas. However, according to the embodiment, a later-mentionedgasification monitor 50 can detect the above mist in situ.

Here, it is noted that the “mist” in this specification does mean notonly an element maintaining a micro-droplet condition as the result thatthe liquid has been vaporized incompletely or vaporized gas has beenliquefied again but liquid and solid elements that may be produced inthe vaporizer or on the downstream side of the vaporizer.

The liquid-material source 20 stores the liquid material containing Hf,for example, HTB (Hf(OtBu)₄) or TDMAH (Hf(NMe₂)₄) as being an organicmetallic compound containing hafnium and delivers the liquid material tothe vaporizer 30 through the material pipe 20 a by appropriate means.

All of these organic metallic compounds are liquids at ambienttemperatures and have respective vapor pressures of relative lowness attemperatures less than their resolving temperatures. Therefore, it iscarried out to vaporize these materials by the vaporizer 30. Forinstance, in case of Hf(OtBu)₄ or Hf(NMe₂)₄, the material is heated toabout 60° C. for its evaporation to produce the reactive gas.

In this embodiment, the above-mentioned process controller 16 controlsall related to the chamber 10, the operations of the power source 15,the exhaust system 18 and the feed control valve 19 a, the operations ofthe carrier-gas control valve 37 and the material flow-control valve 35a on the side of the vaporizer 30 and the heating temperatures of thevaporizing heaters 33 and 34, etc. Consequently, the process controller16 has a function to control all the deposition processes describedlater.

The gasification monitor 50 is arranged in the course of theprocessing-gas pipe 40. The gasification monitor 50 includes a crystalgauge (first pressure gauge) 51, a capacitance manometer (secondpressure gauge) 52 and a monitor controller 53.

As illustrated in FIG. 5, the crystal gauge 51 is formed by a U-shapedquartz oscillator 51 a, electrodes 51 b and 51 c arranged so as tointerleave the quartz oscillator 51 a and a wave generator 51 d forimpressing high frequency waves to the electrodes 51 b and 51 d. Makinguse of a fact that the resonant impedance of the quartz oscillator 51 adepends on its friction with gaseous molecules (gas pressure), thecrystal gauge 51 detects a first pressure Pq of the processing gas inthe processing-gas pipe 40 due to a change in impedance and furtheroutputs the so-detected pressure Pq to the monitor controller 53.

As illustrated in FIG. 6, the capacitance manometer 52 is formed by adiaphragm 52 b arranged in a pressoreceptive chamber 52 a to make adisplacement (deformation) on receipt of the pressure of the processinggas in the processing-gas pipe 40 and a plurality of fixed electrodes 52c opposed to the diaphragm 52 b to detect its displacement (deformation)corresponding to the gas pressure, in the form of a capacity change.Thus, the capacitance manometer 52 is constructed so as to measure asecond pressure Pg of the processing gas by the displacement of thediaphragm 52 b.

Meanwhile, due to the above-mentioned measurement principle, if theprocessing gas contains mist larger than the gaseous molecule, thecrystal gauge 51 is subjected to adhesion of the mist to the quartzoscillator 51 a, so that the impedance is increased that much.Consequently, the crystal gauge 51 outputs a pressure Pq larger than theactual pressure.

On the contrary, in the capacitance manometer 52, even if the processinggas contains mist larger than the gaseous molecule to cause adhesion ofthe mist to the diaphragm 52 b, the adhesion does not influence thedeflection of the diaphragm 52 b. Thus, there is no change in measuredvalues of the pressure Pg of the processing gas.

Therefore, it is possible to regard a difference ΔP between the pressurePq detected by the crystal gauge 51 and the pressure Pg detected by thecapacitance manometer 52 as a parameter representing the quantity ofmist contained in the processing gas. According to this embodiment, themonitor controller 53 calculates the above difference ΔP and furtheroutputs it to the process controller 16 where the later-mentionedoperations of the deposition process are carried out.

One example of the operations will be described below.

First, the operation of the gasification monitor 50 will be describedwith reference to a flow chart of FIG. 3.

At step 101, the monitor controller 53 carries out an initialization tocalibrate measured values appropriately so as to bring a difference ΔPbetween the pressure Pq detected by the crystal gauge 51 and thepressure Pg detected by the capacitance manometer 52 back to zero. Inthis embodiment, since there is no need to detect an absolutemeasurement value of the pressure, the above calibration isaccomplished, for example, by deleting or adding either a measured valueof the former pressure Pq or another measured value of the latterpressure Pg thereby bringing the difference ΔP back to zero.

After the calibration, at step 102, it is executed to receive a pressurePq (measured value) from the crystal gauge 51 and another pressure Pg(measured value) from the capacitance manometer 52. Next, at step 103,it is executed to calculate a difference ΔP. Then, the so-obtaineddifference ΔP is transmitted to the process controller 16 at step 104.At next step 105, it is judged whether the initialization is instructedfrom the process controller 16 or not. If the instruction is present(Yes), then the processes at step 101 and the subsequent steps 102 to104 are carried out repeatedly. While, if the instruction is absent (Noat step 105), the processes at step 102 and the sequent steps 103 and104 are carried out repeatedly.

On the other hand, as illustrated in FIG. 4, the process controller 16commands to allow the monitor controller 53 of the gasification monitor50 to perform the initialization at step 201. Thereafter, when it isdetected that a semiconductor wafer W is loaded into the chamber 10 andmounted on the susceptor 11, the process controller 16 controls thecarrier-gas control valve 37 and the material flow-control valve 35 aabout the vaporizer 30 while depressurizing the chamber 10 by theexhaust system 18, thereby producing a predetermined flow of processinggas consisting of the reactive gas obtained by vaporizing the liquidmaterial and the carrier gas. Continuously, the feed control valve 19 ais opened to introduce the so-produced processing gas into the chamber10 via a number of gas discharging holes 19 c of the shower head 19.

During the above process, since the semiconductor wafer W is heated upto a temperature more than the resolving temperature of the reactive gasby the heater 14 embedded in the susceptor 11, the reactive gas isdissolved on the surface of the semiconductor wafer W, so that thedeposition of a Hf-oxidation film is progressed on the semiconductorwafer W (step 202).

At next step 203, it is judged whether the deposition has been completedor not. When the judgment at step 203 is No, the routine goes to step204 to receive the calculation result of a difference ΔP (i.e. quantityof mist) in the processing-gas pipe 40 from the monitor controller 53.At next step 205, it is first judged whether the difference ΔP is lessthan a first threshold value P1 or not. Note, the first threshold valueP1 is an upper limit (i.e. upper pressure value) on the quantity of mistthat could not cause deposition defects. If the difference ΔP is lessthan the first threshold value P1 (ΔP<P1, Yes at step 205), the routinegoes to step 202 to continue the deposition process.

If the judgment at step 205 is No, that is, the difference ΔP is notless than the first threshold value P1 (P1≦ΔP), the routine goes to step206 where it is judged whether the difference ΔP is less than a secondthreshold value P2 (P1≦ΔP<P2) or not. Note, the second threshold valueP2 is a (pressure) value corresponding to the quantity of mist where itis expected that critical deposition defects are produced certainly andtherefore, the deposition should be cancelled. Thus, when the differenceΔP exceeds the second threshold value P2, the routine goes to step 207to bring the operation of the deposition apparatus to standstill forstoppage of the deposition process.

When the difference ΔP is less than the second threshold value P2(P1≦ΔP<P2, Yes at step 206), the routine goes to step 208 to output awarning indicating the mist being mixed in the processing gas against anoutside operator for equipments or the like. At next step 209, it isjudged whether the present time is a momentum to carry out theabove-mentioned initialization of the difference ΔP at the gasificationmonitor 50 or not. In case of carrying out the initialization of thedifference ΔP at the gasification monitor 50, the routine returns tostep 201 to instruct the initialization of the difference ΔP to thegasification monitor 50 (i.e. execution of step 101 of FIG. 3). While,if the present time is not a momentum to carry out the above-mentionedinitialization, the routine goes to step 202 to continue the depositionprocess until the completion of the deposition process (Yes at step203). Note, when the deposition process is completed, the routine isended.

In an actual deposition, there is a case that the vaporizer 30 isintermittently operated during the deposition process in order to supplythe processing gas intermittently. In such a case, it is possible toaccomplish the initialization at the gasification monitor 50 at thetiming that the processing gas does not contain the reactive gas but thecarrier gas only.

In the above-mentioned embodiment, the output of a warning to theoutside is representative of the operation at step 208. Alternatively,the operation at step 208 may be replaced by a feedback control wherethe quantity of mist detected by the gasification monitor 50 is reducedless than the desirable value P1 on the adjustment of the openingdegrees of the material flow-control valve 35 a and the carrier-gascontrol valve 37 about the vaporizer 30 in order that the quantity ofmist can be usually maintained less than the desirable value P1 duringthe deposition process.

As mentioned above, according to the embodiment, the gasificationmonitor 50 monitors the quantity of mist (ΔP) contained in theprocessing gas supplied to the chamber 10 during the deposition process,at real-time. Therefore, if performing various controls, for example, acontrol where the measured result of the quantity of mist (ΔP) is fedback to the controls of various vaporizing conditions [e.g. flow rate ofcarrier gas (opening degree of the carrier-gas control valve 37), feedrate of the liquid material (opening degree of the material flow-controlvalve 35 a), heating temperatures of the vaporizing heaters 33, 34] inthe vaporizer 30, thereby suppressing the quantity of mist to a lowvalue causing no deposition defect; a control where an outside worker isinformed of the occurrence of mist; a control where the depositionprocess is automatically stopped when the quantity of mist is more thana predetermined threshold value, etc., then it becomes possible toprevent an occurrence of deposition defects due to the mist contained inthe processing gas.

Consequently, it becomes possible to measure the deposition defectsquickly in comparison with a countermeasure for deposition defects dueto mist by inspecting a semiconductor wafer W after the depositionprocess, whereby the productivity at the deposition process can beimproved.

Without being limited to the above-mentioned embodiment, the presentinvention may be modified variously. For instance, although eitherHf(OtBu)₄ or Hf(NMe₂)₄ is employed as the liquid material containing Hfin the above-mentioned embodiment, the same Hf material is notrestricted to these compounds only.

Further, although the present invention is applied to the CVD depositionof Hf in the above-mentioned embodiment, the deposition material is notnecessarily limited to an element Hf. For example, the present inventionis applicable to the CVD depositions of Zr, Si, Cu, Al, etc. by use ofthe following liquid materials of HTB (Zr(OtBu)₄), TDMAS (SiH(NMe₂)₃),TEOS(Si(OCH₂CH₃)₄), Cu(hfac)TMVS, Cu(hfac)ATMS, TMA(Al(CH₃)₃), etc.Further, so long as a processing is carried out by using gas produced byvaporizing the liquid material, the present invention is applicable tothe other film forming processes without being limited to the depositionprocess, such as CVD.

Regarding the vaporizer, not apply only to one that sprays the liquidmaterial into the carrier gas to produce the reactive gas, the vaporizermay be constructed so as to vaporize a liquid material by heat.Alternatively, it may be constructed so as to produce the reactive gasdue to sublimation of a solid material.

Finally, it will be understood by those skilled in the art that theforegoing descriptions are nothing but one embodiment of the disclosedgasification monitor, the method for detecting mist, the depositionmethod and the deposition apparatus and therefore, various changes andmodifications may be made within the scope of claims.

1. A gasification monitor arranged in a gas feeding path between avaporizer for vaporizing a liquid material or a solid material toproduce a processing gas and a processing part where the processing gasis used, the gasification monitor detecting a quantity of mist containedin the processing gas.
 2. The gasification monitor as claimed in claim1, comprising: a first pressure gauge for detecting a first pressure Pqof the processing gas, which is changeable by the quantity of mistcontained in the processing gas; a second pressure gauge for detecting asecond pressure Pg of the processing gas, which is unchangeable by thequantity of mist contained in the processing gas; and a control part fordetecting the quantity of mist contained in the processing gas on abasis of a difference ΔP between the first pressure Pq detected by thefirst pressure gauge and the second pressure Pg detected by the secondpressure gauge.
 3. The gasification monitor as claimed in claim 2,wherein the first pressure gauge has an oscillator arranged in theprocessing gas thereby detecting the first pressure Pq of the processinggas by use of a fact that a impedance of the oscillator changesdependently of the pressure of the processing gas, and the secondpressure gauge has a pressoreceptive part for receiving the pressure ofthe processing gas thereby detecting the second pressure Pg of theprocessing gas on a basis of a deformation of the pressoreceptive partsubjected to the pressure of the processing gas.
 4. The gasificationmonitor as claimed in claim 2, wherein the first pressure gauge is acrystal gauge that includes a quartz oscillator forming the oscillatorthereby detecting the first pressure Pq of the processing gas, and thesecond pressure gauge is a capacitance manometer that includes adiaphragm forming the pressoreceptive part and electrodes opposing thediaphragm and that detects a deformation of the diaphragm in the form ofa change in electrostatic capacity between the diaphragm and theelectrodes thereby detecting the second pressure Pg of the processinggas.
 5. The gasification monitor as claimed in claim 1, wherein theprocessing part is a film forming apparatus that forms a thin film on anobject to be processed by use of a thermal decomposition of theprocessing gas.
 6. The gasification monitor as claimed in claim 1,wherein the processing gas is an organic metallic compound.
 7. A mistdetecting method for detecting mist contained in a gas, comprising thesteps of: detecting a first pressure Pq of the gas, which is changeableby a quantity of mist contained in the gas, by a first method; detectinga second pressure Pg of the gas, which is unchangeable by the quantityof mist contained in the gas, by a second method; and detecting thequantity of mist contained in the gas on a basis of a difference ΔPbetween the first pressure Pq detected by the first method and thesecond pressure Pg detected by the second method.
 8. The mist detectingmethod as claimed in claim 7, wherein the first pressure Pq is detectedby a first pressure gauge having an oscillator arranged in the gas todetect a pressure of the gas by use of a fact that a impedance of theoscillator changes dependently of the pressure of the gas, and thesecond pressure Pg is detected by a second pressure gauge having apressoreceptive part for receiving the pressure of the gas to detect thepressure of the gas on a basis of a deformation of the pressoreceptivepart subjected to the pressure of the gas.
 9. The mist detecting methodas claimed in claim 8, wherein the first pressure gauge is a crystalgauge that includes a quartz oscillator forming the oscillator therebydetecting the first pressure Pq of the processing gas, and the secondpressure gauge is a capacitance manometer that includes a diaphragmforming the pressoreceptive part and electrodes opposing the diaphragmand that detects a deformation of the diaphragm in the form of a changein electrostatic capacity between the diaphragm and the electrodesthereby detecting the second pressure Pg of the processing gas.
 10. Themist detecting method as claimed in claim 7, wherein the processing gasis an organic metallic compound used by a film forming apparatus.
 11. Afilm forming method for forming a thin film on an object to be processedby thermally decomposing a processing gas obtained by vaporizing aliquid material or a solid material, the film forming method comprisingthe steps of: monitoring a quantity of mist contained in the processinggas; and controlling vaporizing conditions of the liquid material or thesolid material in a manner that the quantity of mist decreases.
 12. Afilm forming method for forming a thin film on an object to be processedby thermally decomposing a processing gas obtained by vaporizing aliquid material or a solid material, the film forming method comprisingthe steps of: monitoring a quantity of mist contained in the processinggas; and either outputting a warning or stopping a film forming processwhen the quantity of mist exceeds a predetermined threshold value. 13.The film forming method as claimed in claim 11 or claim 12, wherein themonitoring step comprises the steps of: detecting a first pressure Pq ofthe gas, which is changeable by a quantity of mist contained in theprocessing gas, by a first method; detecting a second pressure Pg of thegas, which is unchangeable by the quantity of mist contained in theprocessing gas, by a second method; and detecting the quantity of mistcontained in the processing gas on a basis of a difference ΔP betweenthe first pressure Pq detected by the first method and the secondpressure Pg detected by the second method.
 14. The film forming methodas claimed in claim 11 or claim 12, wherein the first pressure Pq isdetected by a first pressure gauge having an oscillator arranged in thegas to detect a pressure the processing gas by use of a fact that aimpedance of the oscillator changes dependently of the pressure of theprocessing gas, and the second pressure Pg is detected by a secondpressure gauge having a pressoreceptive part for receiving the pressureof the processing gas to detect the pressure of the processing gas on abasis of a deformation of the pressoreceptive part subjected to thepressure of the processing gas.
 15. The film forming method as claimedin claim 14, wherein the first pressure gauge is a crystal gauge thatincludes a quartz oscillator forming the oscillator thereby detectingthe first pressure Pq of the processing gas, and the second pressuregauge is a capacitance manometer that includes a diaphragm forming thepressoreceptive part and electrodes opposing the diaphragm and thatdetects a deformation of the diaphragm in the form of a change inelectrostatic capacity between the diaphragm and the electrodes therebydetecting the second pressure Pg of the processing gas.
 16. The filmforming method as claimed in claim 11 or claim 12, wherein theprocessing gas is an organic metallic compound used by a film formingapparatus.
 17. A film forming apparatus comprising: a processing partfor forming a thin film on an object to be processed by use of aprocessing gas; a vaporizer for vaporizing a liquid material or a solidmaterial to supply the processing part with the processing gas; and agasification monitor arranged in a gas feeding path for the processinggas between the vaporizer and the processing part, for detecting aquantity of mist contained in the processing gas.
 18. The film formingapparatus as claimed in claim 17, further comprising a processcontroller that controls at least either one of the operation of thevaporizer and the operation of the processing part, on a basis of thequantity of mist obtained by the gasification monitor.
 19. The filmforming apparatus as claimed in claim 17, wherein the gasificationmonitor includes: a first pressure gauge for detecting a first pressurePq of the processing gas, which is changeable by the quantity of mistcontained in the processing gas; a second pressure gauge for detecting asecond pressure Pg of the processing gas, which is unchangeable by thequantity of mist contained in the processing gas; and a control part fordetecting the quantity of mist contained in the processing gas on abasis of a difference ΔP between the first pressure Pq detected by thefirst pressure gauge and the second pressure Pg detected by the secondpressure gauge.
 20. The film forming apparatus as claimed in claim 18,wherein the first pressure gauge has an oscillator arranged in theprocessing gas thereby detecting the first pressure Pq of the processinggas by use of a fact that a impedance of the oscillator changesdependently of the pressure of the processing gas, and the secondpressure gauge has a pressoreceptive part for receiving the pressure ofthe processing gas thereby detecting the second pressure Pg of theprocessing gas on a basis of a deformation of the pressoreceptive partsubjected to the pressure of the processing gas.
 21. The film formingapparatus as claimed in claim 17, wherein the first pressure gauge is acrystal gauge that includes a quartz oscillator forming the oscillatorthereby detecting the first pressure Pq of the processing gas, and thesecond pressure gauge is a capacitance manometer that includes adiaphragm forming the pressoreceptive part and electrodes opposing thediaphragm and that detects a deformation of the diaphragm in the form ofa change in electrostatic capacity between the diaphragm and theelectrodes thereby detecting the second pressure Pg of the processinggas.
 22. The film forming apparatus as claimed in claim 17, wherein theprocessing part is adapted so as to perform a process of forming a thinfilm on an object to be processed by use of a thermal decomposition ofthe processing gas.
 23. The film forming apparatus as claimed in claim17, wherein the processing gas is an organic metallic compound.